Frequency mixers or mixers are a key component in radio frequency (RF) transceiver front-ends and are ubiquitously used in wireless communication system components including, for example, RF Identification (RFID) transceivers, RF tags, and RF sensor networks. Complementary metal-oxide-semiconductor (CMOS) mixers are a cost effective solution for many RF mixer applications. Nevertheless, the active mixers (e.g., mixers with trans-conductance stage to provide conversion gain) suffer from high noise figure (NF), poor linearity, and high power consumption, while the passive mixers (e.g., mixers with no trans-conductance stage and thus no conversion gain) suffer from high conversion loss.